Take this as constructive criticism, but when I see “for all languages”, I’m immediately skeptical, and then annoyed when the languages I’m interested in aren’t supported. Saying “Linting and fixing code for tons of languages” sounds just as good, and is more honest.

I do see your point but when coala was started the goal was to have one liter interface to unite them all. We are constantly working towards extending support for more languages by adding more linters to our list.
If you don’t see the languages you want supported by coala then you can make an issue over here: https://github.com/coala/coala-bears/issues

coala provides a command line interface to deal with various linter tools (known as coala bears) through a single configuration file for the whole project. This saves users time since they don’t have to learn how to configure multiple linters for their project.
coala uses two kinds of bears

Linter Bears that are python wrappers around external linter tools (for e.g. the bear for JavaScript Standard Style in coala is called as JSStandardsBear)

Native Bear that are python implementations of a specific code analysis algorithms plugged into coala without using any external tools.

Another other aspect of coala that makes it a very exciting project to work with is the beginner-friendly community that makes it easy for amateur developers to get started with contributing to open source software.